Method and apparatus for mixing, spraying and placing cementitious materials

ABSTRACT

There is provided an improved composition for rapid setting, sprayable cementitious material, as well as improved processes and systems for mixing and placing such materials. The composition comprises a sprayable mixture of cement forming ingredients, such as silicon dioxide, magnesium oxide, and an aqueous metal phosphate solution. The process for mixing and placing such a composition uses serially connected dry material feed receptacles which are independently pressurizable and are isolatable from ambient conditions after loading to provide substantially increased throughput volume. The receptacles communicate the composition to a fluidizing element in which the material is fluidized before being formed into a slurry and atomized. Alternatively, dry and slurried material can be conveyed in a cavity pump under high pressure to achieve substantially increased throughput volume.

BACKGROUND OF THE INVENTION

This invention relates to sprayable, rapid setting cementitiousmaterials and to methods of making and applying such materials.

Cementitious materials are used extensively in the construction industryas pavements and/or surface coatings for infrastructures such asroadways, swimming pools, bridges, walls, tunnels and other structureswhich are exposed to the elements and/or to repeated heavy use. Manyapplications require rapid curing of the cementitious materials.

In a typical cement making and placing process, dry materials are addedto a mixing chamber through an open hopper, to which additional drymaterial is fed as needed to maintain a continuous process. Apressurized gas stream, such as compressed air, is introduced into themixing chamber to aerate, tumble and convey the dry materials throughthe mixing chamber. The gas stream is also used to blend a liquidcomponent, also introduced under pressure, with the dry materials toform a slurry. The gas stream is typically introduced and maintained ata relatively low pressure (i.e., up to about 15 psi) through the use ofvarious constricting devices, such as static mixers, venturi eductorsand transvectors.

One technical problem that must be overcome is to avoid constriction ofthe mixing device. If constriction is excessive, the dry materials canbe blown back into the material hopper, causing hazardous dustingconditions. Further, inadequate gas stream pressure can cause the slurryto clog the mixing equipment and impede movement of the slurry throughthe mixing chamber. Attempts to force the material through thedispensing equipment by increasing the gas stream pressure can fail froman inability to maintain sufficient pressure in the mixing chamber whenit is open to ambient conditions.

U.S. Pat. No. 4,355,060 to Cornwell discloses a high temperaturecementitious material comprising a mixture of magnesium oxide, fly ash,finely divided mineral aggregates and aqueous ammonium phosphatesolutions. Cementitious material compositions which include ammoniumphosphates, such as the composition disclosed in Cornwell '060, arecharacterized by an offensive odor that is produced during cure of thematerial and the resulting release of ammonia.

U.S. Pat. No. 4,390,371 to Cornwell discloses a method for mixing,spraying and placing such a cementitious material. The method usesstatic in-line mixers and an open hopper to hold blended dry material.The material is then transported with compressed air to the staticmixing system, for example, by using a transvector or a venturi eductor.

Specialized equipment is necessary to make and place rapid setting,sprayable cementitious materials. In particular, the use of staticin-line mixers for preparing and placing such materials can beproblematic. Rapid setting compositions require faster mixing and fastertransport through mixing and spraying equipment in order to avoid curingand hardening of the material while it is still in the equipment. Thus,these compositions must be mixed and moved through the equipment atrelatively greater speeds and under relatively greater fluid pressures.Conventional cement mixing equipment is not designed to accommodate theincreased fluid pressures required to mix and place these rapid settingcompositions. For example, the use of air pressures greater than about15 pounds per square inch (psi) in conventional processing equipment cancause problems such as leakage and mechanical seals, uncontrolleddusting of the dry ingredients, tunneling of compressed air throughslurries and dry ingredients, and clogging of hoses with slurry or dryingredients that are not adequately mixed or transported in the fluidstream. Further, the addition of fibrous reinforcing material, such asfiberglass, as a dry ingredient results in flocking or fluffing of thefiberglass within the static mixer and other interstices of theequipment. The result is incomplete mixing of the material and,consequently, nonuniformity and reduced strength of the final product.

The use of conventional air pressures to mix and place rapid settingcementitious compositions does not sufficiently propel either the drymaterial through the mixing equipment or the slurried material through aconstricting device for satisfactory placement of the material. Further,only objects which are located immediately adjacent to the constrictingdevice can be spray-coated using conventional air pressures.

It is therefore an object of the invention to provide an improved systemfor preparing and dispensing rapid setting cementitious materials. It isa further object of the invention to provide an improved rapid settingcementitious composition. Another object of the invention is to providean apparatus for making and placing rapid setting cementitiousmaterials. These and other objects will be apparent from the descriptionwhich follows.

SUMMARY OF THE INVENTION

The invention relates to rapid setting cementitious materials andmethods of making and placing such materials. In one aspect of theinvention, there is provided a composition for a rapid setting,sprayable cementitious material. The composition comprises up to about200 parts by weight silicon dioxide, up to about 50 parts by weightmagnesium oxide, and approximately 10 to 150 parts by weight of anaqueous monometal phosphate solution.

The composition can further include up to about 200 parts by weight ofat least one metallic oxide selected from the group consisting of theoxides of calcium, aluminum, iron, potassium, titanium and sodium, up toabout 50 parts by weight calcium carbonate, and up to about 30 parts byweight of preselected lengths of binderless fiberglass fibers, can beadded with the dry component.

The aqueous monometal phosphate solutions are selected for their abilityto promote a rapid cure without releasing ammonia. They can include, forexample, monoaluminum phosphate, monomagnesium phosphate and monocalciumphosphate.

In another aspect of the invention, there is provided a continuousprocess for making a rapid setting, sprayable cementitious material. Thedry materials described above are added to a first receptacle which iscontrollably connected with and disposed upstream of a secondreceptacle. During loading of the dry material, the first receptacle isopen to ambient conditions and is isolated from the second receptacle.The second receptacle is fluidically connected with a fluidizingelement, in which a pressurized gas fluidizing stream establishes thepressure of the first and second receptacles during the process.

Alter the dry material is loaded into the first receptacle, the firstreceptacle is isolated from ambient conditions and then opened to thesecond receptacle to permit equilibration of the pressures within thetwo receptacles and to permit the transfer of the dry material from thefirst receptacle to the second receptacle. The dry material in thesecond receptacle is then continuously transferred to a fluidizingconduit in which it is fluidized in a pressurized gas stream introducedvia a gas entry port in the fluidizing conduit. The fluidized materialis transported to an impingement element which is disposed downstream ofthe fluidizing element. An aqueous phosphate solution is then introducedunder pressure to the fluidized material in the fluidizing element justupstream of the impingement element. The aqueous phosphate solutioncombines with the dry component in the impingement element to form aslurry. The slurry is then atomized through a constricting element whichis disposed downstream of the impingement element to yield a sprayable,rapid setting cementitious material.

In another aspect of the invention, there is provided an alternativecontinuous process for making a sprayable, rapid setting cementitiousmaterial. In this process, a dry component as described above isintroduced to an inlet port of a cavity pump. During pump operation thedry component is mixed and transported through the pump. About 10 to 150parts by weight of an aqueous phosphate solution is then introducedunder pressure into a portion of the dry component in an interiorchamber of the cavity pump to form a slurry. The slurry is mixed andatomized to form a sprayable, rapid setting cementitious material.

According to another aspect of the invention, there is provided amaterial mixing and dispensing system for continuously making anddispensing a rapid setting sprayable cementitious material. The systemincludes at least one paired first and second receptacle, the firstreceptacle being controllably connected with and disposed upstream ofthe second receptacle. The paired first and second receptacles areindependently pressurizable by introduction of a pressurized gasthereto. The second receptable communicates with a fluidizing element inwhich the dry material is fluidized and transported in a pressurized gasstream. The fluidizing element includes a conduit, a gas entry port forintroducing a fluidizing stream, and a liquid entry port for introducinga pressurized liquid. The system further includes an impingement elementdisposed downstream of the fluidizing element for mixing the drymaterial with the liquid to form a slurry, and a constricting elementfor dispersing the slurry to obtain a sprayable cementitious material.

In one embodiment, the paired first and second receptacles areindividual hoppers. In an alternative embodiment, the paired first andsecond receptacles are formed of portions of a single flexible conduit,each conduit comprising separable first and second receptacles.Preferably this embodiment involves the use of several adjacent conduitsthat communicate at a downstream portion thereof with a commonfluidizing conduit.

The gas entry port in the fluidizing conduit is preferably disposed inan upstream portion of the fluidizing conduit. The liquid entry port inthe fluidizing conduit is typically located downstream from the gasentry port.

In one embodiment the impingement element comprises a static mixer, inwhich the slurry is mixed prior to atomization. In an alternativeembodiment, the impingement element comprises a separate nozzle orsimilar constricting device which creates turbulence in the slurry,thereby mixing it prior to atomization.

The constricting or atomizing element can be in the form of a singlenozzle through which the slurry passes under pressure to be atomized.Alternatively, the constricting element can further include a separateair jet which impinges on the atomized cementitious material exiting thenozzle to further atomize the material.

The material mixing and dispensing system can further include a chopperunit disposed downstream of the constricting element for choppingfiberglass roving into preselected lengths. An auxiliary air jetdisposed between the chopper unit and the constricting element fluidizesthe chopped fiberglass roving and disperses it into the atomizedcementitious material.

The term "cementitious material", as used herein, refers to anycomposition comprising a mixture of a dry component, which can includerelatively fine active ingredients and relatively coarse inactiveingredients, and a liquid component which reacts with the active dryingredients to form a concrete-type material which, when fully cured, isextremely durable and resistant to thermal and mechanical stresses andto attack by corrosion, moisture and chemicals. The term "rapidsetting", as used herein, refers to the ability of the material toundergo a rapid reaction upon contact of the active ingredients with theliquid component to form a material which is substantially cured withinone to several minutes. The term "sprayable", as used herein, refers tothe ability of the material, prior to full cure, to be atomized underpressure through a constricting device and to be sprayed onto a desiredsubstrate. The terms "isolatable" or "isolated", as used herein, referto vessels which are sealable or sealed, respectively, to prevent lossof fluid, whether gas, liquid or even powdered solid material.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the invention,reference should be made to the following detailed description and theaccompanying drawings, in which:

FIG. 1 is a schematic diagram of a material mixing and dispensing systemused in a continuous process for making a sprayable, rapid settingcementitious material according to one embodiment of the invention;

FIGS. 2 and 3 are schematic diagrams of alternative systems andprocesses for making a sprayable, rapid setting cementitious materialaccording to the invention; and

FIG. 4 is a schematic illustration of the operation of the dry materialfeed portion of the material mixing and dispensing system illustrated inFIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides, inter alia, an improved composition for a rapidsetting, sprayable cementitious material. The composition comprises adry component which can include active and inactive dry ingredients, anda liquid component comprising an aqueous metal phosphate solution. Theterm "active", as used herein, refers to an ingredient of a cementitiousmaterial which reacts exothermically to cure the material. Activeingredients are generally fine particles which easily pass through a 100mesh screen. The term "inactive", as used herein, refers to aningredient in a cementitious material which is not essential to thecuring reaction but instead acts as a filler or aggregate. Inactiveingredients are generally relatively coarse materials having a particlesize greater than 100 mesh.

The active ingredients include calcium carbonate and one or moremetallic oxides selected from the group consisting of the oxides ofcalcium, aluminum, iron, potassium, titanium and sodium. The inactiveingredients include silicon dioxide and, optionally, fiberglass fibers.

The silicon dioxide is added in an amount of up to about 200 parts byweight of the mixture. It can be in the form of a flour, a powder, acoarse sand, and/or a relatively large aggregate. The particle size andpurity of the silicon dioxide can vary widely, i.e., from less than 325mesh (0.0017 inch) to pea gravel (1/4"), depending on the desiredcharacteristics of the resulting cementitious material. Silicon dioxideis generally added in the form of relatively coarse sand, i.e., wellover 100 mesh in particle size. Silicon dioxide is commerciallyavailable from a number of sources, including U.S. Silica (BerkeleySprings, W.Va.).

Magnesium oxide is an essential active ingredient which is added in anamount of up to about 50 parts by weight to promote a rapid cure. It isgenerally well under 100 mesh in particle size. Magnesium oxide can beobtained, for example, from Martin Marietta (Hunt Valley, Md.).

The metallic oxides typically are added in a total amount of up to about200 parts by weight. They are active ingredients and are generally wellbelow 100 mesh in particle size. The metallic oxides are commonly foundin virtually every type of naturally occurring rock, sand and/ormineral. The presence, relative amounts and particle sizes of thevarious metallic oxides will depend ultimately on the desired cure andstrength characteristics or the resulting cementitious material. Forexample, calcium oxide, which slows the cure, can be added in amounts ofup to 50 parts by weight. Aluminum oxide can be added in amounts of upto about 100 parts by weight, and the remaining oxides can each be addedin amounts of up to about 10 parts by weight. These metallic oxides areavailable commercially from many chemical suppliers, and one of ordinaryskill in the art will readily understand the metal oxides and quantitiesor metal oxides to be used to impart desired properties.

Calcium carbonate is an active ingredient which is added in an amount ofup to about 50 parts by weight. It promotes frothing of the resultingcementitious material, thereby increasing porosity and reducing weight.The calcium carbonate is generally well below 100 mesh in particle sizeand can be obtained, for example, from ECC America (Sylacauga, Ala.).

Optionally, up to about 30 parts by weight of precut lengths ofbinderless fiberglass fibers can be added. The term "binderless", asused herein, refers to the absence of any organic binder, such assilane, in the fiberglass stranding.

The presence of short fiberglass fibers in the cementitious materialincreases the strength of the cementitious material withoutsignificantly increasing the weight per unit volume of the material.Binderless fiberglass fibers are commercially supplied in relativelyshort lengths (i.e., less than one inch long and preferably from 1/4" to1/2") and can be added with the dry component. Binderless fiberglass isavailable, for example, from PPG Industries or from Owens Corning.

The liquid component comprises about 10 to 150 parts by weight of anaqueous metal phosphate solution. Aqueous metal phosphate solutions arebelieved to produce a stronger cementitious material than is obtainedwhen ammonium phosphate is used as the liquid component. Further,although water itself can be used as the liquid component in makingcementitious materials, the rapid setting characteristic of thismaterial requires the use of an aqueous phosphate solution as the liquidcomponent. The metal phosphate solutions used with the present inventionare environmentally acceptable in virtually all cement-making processesdue to their aqueous nature. A further advantage is that they do notrelease noxious fumes during the reaction with the active dryingredients.

Exemplary metal phosphates include monoaluminum phosphate, monomagnesiumphosphate and monocalcium phosphate, in which the metal phosphate ispresent at about 50% concentration. It can be obtained by reducing ametal polyphosphate powder to a monometal phosphate in an aqueousphosphoric acid solution. Suitable metal phosphate solutions are alsocommercially available from Albright & Wilson (Richmond, Va.). Aqueousmonoaluminum phosphate is currently the preferred liquid component.

The invention further provides improved processes for making rapidsetting cementitious materials which can be sprayed onto a variety ofsubstrates. In one embodiment, the process employs serially arranged andcontrollably connected first and second receptacles which are isolatablefrom ambient conditions and which are also independently pressurizable.Such receptacles permit continuous dry material transfer at pressuressubstantially in excess of the pressures attainable when rotary airlockvalves are used according to previously known techniques.

According to the process of the invention, the first receptacle isfilled with a dry material as previously described. During loading ofthe dry material into the first receptacle, the second receptacle, whichis pressurized to a selected uniform pressure, is isolated from thefirst receptacle. After the first receptacle has been fully loaded withdry material, it is selectively isolated from ambient conditions and isselectively opened to the second receptacle to permit the tworeceptacles to equilibrate. The dry material is thus transferred fromthe first receptacle into the second receptacle by gravity flow througha rotary valve or other conventional metering device.

The second receptacle is serially connected to a fluidizing elementwhich includes a conduit and a port or jet for introducing a pressurizedgas to fluidize the dry material and establish the pressures of thefirst and second receptacles. The dry material is allowed to flow bygravity feed, in amounts controlled by a metering device, from thesecond receptacle into the fluidizing element where it is fluidized in apressurized gas stream. The fluidized dry material is then transportedto an impingement element disposed downstream of and connected with thefluidizing element.

An aqueous phosphate solution as described above is then introducedunder pressure into the fluidized dry material in the fluidizing elementupstream of the impingement element. The liquid solution typically isintroduced at a pressure of approximately 50 to 70 psi (absolute), orpreferably about 15-20 psi greater than the pressure of the fluidizingstream. The force of the incoming liquid stream, combined with theturbulence of the fluidized dry materials in the fluidizing stream,causes mixing of the dry and liquid components in the impingementelement to form a slurry. The slurry is transported through theimpingement element at a selected pressure, typically between 30 and 50psi, to a constricting element, such as a nozzle or other reduceddiameter orifice, to be atomized and dispensed in a spray.

In a preferred embodiment air is the fluidizing vehicle. However, othergases can be used, especially if one or more properties of the gas usedare beneficial to stabilize or slow the reaction between the dry andliquid components to permit the material to pass completely through theequipment before curing begins. Examples of such gases include carbondioxide, argon and nitrogen.

The reaction between the dry and liquid components used to form thecementitious material is exothermic. The heat released during thereaction can be dissipated or cooled by employing a cooled gas stream.Alternatively, the gas can be introduced at room temperature.

The first and second receptacles can be individual units, such asconventional bins or hoppers, which are isolatable from each other andfrom ambient conditions via sealable valves or lidded ports. The bins orhoppers can be of any conventional type which meet the applicableindustry standards for safety, design and construction. The dimensionsof the bins will be determined by space limitations and the desiredvolume of material to be produced.

In one embodiment, the controllable valves between the receptacles andthe fluidizing element can be, for example, conventional rotary airlockvalves. The rotary valves in this instance function as simple meteringdevices because there is no pressure differential on either side of thevalve, and thus no airlock. As a result there are no delivery pressurelimitations imposed upon the rotary valves.

The fluidizing conduit is typically an air hose or other conduit intowhich the dry material flows by gravity feed and in which the drymaterial is fluidized in a pressurized gas stream. The fluidizing streamtransports the dry material through the fluidizing conduit to theimpingement element.

The impingement element can be, for example, a static mixer or similardevice which includes stationary vanes arranged in a geometricalconfiguration against which a pressurized fluid or slurry impinges as itpasses through the device. The force of the impinging fluid against thestationary vanes creates turbulent flow, thereby mixing the impingingfluid. Preferred static mixers include the KMA series six-element modelsavailable from Chemineer (N. Andover, Ma.).

Alternatively, the impingement element can be a nozzle or similarconstricting device which also creates turbulent flow in a pressurizedstream flowing through it. This type of constricting device containsneither stationary vanes nor moving parts. Instead, turbulent flow iscreated, and the fluid is mixed, when a pressurized fluid impingesagainst the interior walls of the constricting device which narrow toform the reduced diameter opening characteristic of such devices.Preferred constricting devices include nozzles and venturi tubes.

The constricting element can be a nozzle, venturi tube or other reduceddiameter orifice. Commonly used nozzles have 1/2", 3/4" and 1" orifices.Such constricting devices do not contain stationary vanes, as in staticmixers, but instead impart turbulence to a material stream passingtherethrough by causing the particles within the stream to impinge uponthe narrowed walls of the constricting device.

The constricting element can be a single nozzle through which thecementitious material is dispensed. It can also include a separate airjet which impinges compressed air upon the atomized cementitiousmaterial at a preselected angle to further atomize the cementitiousmaterial. Such a separate air jet is typically arranged to deliver airto the atomized cementitious material at an absolute pressure of about25 to 40 psi from one or more orifices. Preferably, this air jet isdelivered at a relatively low angle of incidence (e.g., less than 45°)with respect to the output from the constricting element.

The liquid jet, static mixer and nozzles can all vary in diameter tomeet the requirements of a particular material composition, viscosity,flow rate and spray pattern. Typically, the liquid jets range in sizefrom 1/16" through 9/32". The static mixers can vary from 3/4" diameterto 11/2" diameter, and the nozzles can vary from 1/2" to 1". The mostpreferred combination of component sizes is a 7/64" liquid jet with a 1"diameter static mixer and a 3/4" nozzle.

FIG. 1 illustrates schematically a material delivery device and processof the invention according to one embodiment thereof, in which firstreceptacle R1 is serially arranged and controllably connected withsecond receptacle R2. Receptacle R1 includes a hinged lid (not shown)for sealing the first receptacle from ambient conditions. A valveelement V1 is disposed between the first and second receptacles R1, R2for delivering dry material from R1 to R2. With valve element V1 closedand the lid to R1 open, dry material 10 is fed into the first receptacleR1. After the first receptacle R1 is filled with dry material 10, thehinged lid to R1 is closed, thereby isolating R1 from ambientconditions.

The second receptacle R2 is fluidically connected with fluidizingconduit C1 by means of a second valve element V2. The fluidizing conduitC1 includes means for introducing a fluidizing gas 20 thereto. Thus whenvalve element V2 is open the second receptacle R2 is at substantiallythe pressure of the gas 20 in the fluidizing conduit C1.

Valve element V1 is opened to permit transfer of the dry material 10from the first receptacle R1 to the second receptacle R2. At this stageof the process the first receptacle R1, the second receptacle R2 and thefluidizing conduit C1 are all at substantially equal pressure, i.e., thepressure of the pressurized gas stream 20 in the fluidizing conduit C1.Thus, the dry material 10 flows by gravity feed from the firstreceptacle through valve element V1 and into the second receptacle R2.Similarly, the dry material 10 flows by gravity feed from the secondreceptacle R2 through valve element V2 and into the fluidizing conduitC1.

A pressurized gas stream 20 is introduced into the fluidizing conduit C1to fluidize the dry material 10 and convey it through C1 to animpingement element M. A liquid 30, which can be an aqueous phosphatesolution as previously described, is introduced under pressure through ajet to the fluidized dry material 20 in the fluidizing conduit C1 justupstream of the impingement element M. The liquid jet 30 impinges uponthe fluidized dry material 10 and forms a slurry 40. The slurry 40 istransported through the impingement element M by the fluidizing gasstream 20 and is mixed by the impingement of the slurry 40 on theinternal structure of the impingement element M. The slurry 40 thenpasses through a constricting element 50 to be dispersed as atomizedcementitious material 45.

FIG. 1 also illustrates the addition of short lengths of choppedfiberglass roving 80 to the atomized cementitious material 45.Fiberglass roving is manufactured as a bundle of continuous fiberglassstrands which are either bundled as parallel fibers or twisted to form amulti-ply strand. The diameter of a single fiberglass fiber is extremelysmall, i.e., on the order of a few ten-thousandths of an inch.Fiberglass roving can thus contain up to several thousand individualfiberglass strands which are bound together in parallel strands (roving)or in twisted strands (yarn). The fiberglass roving is bound with anorganic binder, such as a silane or starch compound, to promoteadherence of the fiberglass strands to one another and to othermaterials in the mixtures to which the roving or yarn is added.

The roving is typically added to the cementitious material relativelylate in the cement making process, i.e., alter the slurry stage. Theroving is typically chopped to a desired length, preferably in 1" to 3"lengths, by an in-line chopper unit and added either to the slurry or tothe atomized cementitious material. In the embodiment shown in FIG. 1,the fiberglass roving 80 can be chopped into preselected lengths by achopper unit 90, which is disposed downstream of the constrictingelement 50. The chopped fiberglass roving 80 can then be blown into theatomized cementitious material 45 in a pressurized air jet 22 from asuitably disposed separate nozzle 95.

Alternatively, individual fibers can be added to the atomized materialin a similar manner.

In another embodiment, the paired, isolatable first and secondreceptacles can be formed in separate portions of a single flexibleconduit. Preferably, as illustrated in FIG. 4, several flexible conduits500 are disposed adjacent to each other and in communication with acommon fluidizing conduit 300. In this embodiment, the portions offlexible conduit can be isolated from one another with conventionalmeans, such as a pneumatic or hydraulic tourniquet, or a mechanicalpinching element, or other controllable sealing element.

As shown in FIG. 4, flexible conduit 500 includes an entry port 501, ahinged lid L movably disposed over the entry port, a first portion 510(analogous to first receptacle R1), a second portion 520 downstream ofthe first portion (analogous to second receptacle R2), and an exit port530 leading to a fluidizing conduit 300 (analogous to C1). The variousportions of conduit 500 are separable and sealable from one another byselectively closable scaling elements 600 (analogous to valve elementsV1 and V2). Sealing elements 600 can be in the form of pinch bars orother conventional devices which can be driven, for example, bymechanical, electrical, hydraulic or pneumatic controls. The sealingelements 600 effectively seal the first portion 510 from ambientconditions and also seal the second portion 520 from the fluidizingconduit 300. A typical flexible conduit can be made from, for example,flexible plastic tubing, and a typical pinch bar can be made from, forexample, 3/4" round bar stock.

Portion 4A of FIG. 4 shows the flexible conduit 500 with the upper pinchbars 600 closed, the lower pinch bars 600 open and the first portion 510of the conduit full of dry material 10. At this stage of the process thefirst portion is open to ambient conditions and isolated from thedownstream portions, which are pressurized to a selected uniformpressure by means of pressurized gas stream 20 flowing through thefluidizing conduit 300.

Portion 4B of FIG. 4 illustrates that the lower pinch bars 600 areclosed in preparation for transfer of dry material 10 from the firstportion 510 into the second portion 520. The second portion 520 ispressurized to the pressure of the pressurized gas stream 20 in thefluidizing conduit 300.

As shown in portion 4C of FIG. 4, the upper portion 510 has beenisolated from ambient conditions by engagement of the lid L over theentry port 501. The upper pinch bars 600 are then opened to permit thefirst and second portions of the conduit to equilibrate and to permitthe dry material 10 to flow by gravity into the second portion 520 ofthe conduit. At this stage of the process the first and second portionsof the conduit are uniformly pressurized to the pressure of thepressurized gas in the fluidizing conduit 300.

In portion 4D of FIG. 4 the first portion 510 of the conduit is to berefilled with dry material 10. Hinged lid L is disengaged from the entryport, thereby opening the first portion 510 to ambient conditions. Theupper pinch bars 600 are closed again so that the second portion 520 andthe fluidizing conduit 300 remain at substantially equal pressures andare isolated from ambient conditions. Dry material 10 is then added tothe first portion 510, and the cycle is repeated to maintain acontinuous delivery of dry material 10 to the fluidizing conduit 300.Accordingly, portion 4E of FIG. 4 illustrates the same condition asshown in portion 4A of FIG. 4.

Upon exiting the flexible conduit 500, the dry material 10 passes intothe fluidizing conduit 300, where it is fluidized within and transportedby a pressurized gas stream 20 entering the fluidizing conduit 300 froma separate jet 301. The pressurized gas 20 can be introduced into thefluidizing conduit 300 at any convenient angle. However, it is preferredto introduce the pressurized gas stream from an upstream portion of thefluidizing conduit and as nearly parallel as possible to thelongitudinal axis of the fluidizing conduit, i.e., substantiallyparallel to the ultimate direction of material transport through thefluidizing conduit.

As shown in portion 4F of FIG. 4, a liquid component 30 is introducedthrough a jet 31 into the fluidized dry material 10 in the fluidizingconduit 300 just upstream of an impingement element M to form a slurry40 with the dry material 10. The slurry 40 is conveyed through theimpingement element M to a constricting element 50, which dispenses thecementitious material 45 in atomized form. The impingement element M canbe a static mixer or a nozzle, as previously described.

Chopped lengths of fiberglass roving 80 can be fluidized in a separateair jet 22 downstream of the constricting element 50 and added to theatomized cementitious material 45, as previously described.Alternatively, short lengths of binderless fiberglass fibers 85 can beadded with the dry material 10 to the entry port 501 of the conduit 500,as described above.

The flexible conduit 500 is preferably a durable, flexible polymerictubing, such as Tygon® tubing. Typical tubing diameters include 1" and11/2"; however, the diameter and length of the tubing can be of anydimension which will provide the desired volume of dry materialdelivery. It is preferred to employ multiple conduits to provide asmooth, uninterrupted material delivery feed to the fluidizing conduit.The use of a greater number of flexible conduits generally will resultin a more uniform delivery, of dry material. A typical material mixingand dispensing device according to this embodiment of the inventioncould include, for example, up to eight flexible conduits arranged inparallel, each feeding into a single fluidizing conduit.

Other configurations of serially arranged receptacles which areisolatable from one another and from ambient conditions to achievecontinuous dry material transfer can also be employed.

One advantage of the process of the present invention is that greatermaterial delivery pressures and flow rates can be obtained. Where priorart systems are employed, material delivery pressures are limited toabout 15 psi, and material throughput is limited to about 215 cubic feetper minute. In contrast, with the present invention, substantiallyincreased material delivery pressures (i.e., up to 100 psi or higher)are attainable, and material throughput can exceed 1,700 cubic inchesper minute. In addition, higher material delivery pressures enable theaddition of short lengths of binderless fiberglass fibers 85 as a drymaterial to the first receptacle, as well as to the atomizedcementitious material 45 after it exits the constricting element 50.

FIGS. 2 and 3 illustrate an alternative embodiment of the invention, inwhich a cavity pump is used to transport the dry component 10 and theslurried material 40 and to provide substantially increased materialdelivery pressures. A cavity pump has a power-driven rotating element,or rotor, and a stationary element, or stator, which are structurallycomplementary to one another. In one embodiment, the rotor has a singlehelix shape and the stator has a double helix shape. In addition, thestator and rotor are typically made of different materials, the rotortypically being made of a metallic material and the stator being made ofa more resilient material, such as an elastomer. The rotor and statormate in an interference or compression fit. This close fit between therotor and stator creates a series of temporary, or transient, cavitiesbetween the vanes of the rotor as it rotates and moves linearly withinthe stator. Pumping action occurs when the rotor turns eccentricallywithin the stator. Generally a liquid or slurry enters the cavity formedat the pump inlet and progresses linearly through the pump with movementof the rotor to the pump outlet. The resulting non-pulsating output flowis directly proportional to the speed of the rotor.

FIG. 2 illustrates one process of the invention in which a cavity pump70 is used. In this embodiment a cavity pump 70 having multipletransient cavities 70a-70d is employed to mix and transport the drymaterial 10 and the slurried material 40 to an impingement element M tobe mixed before passing through a constricting element 50 to beatomized. The dry component 10 is added to the inlet cavity 70a of thepump and is tumbled as the rotor moves through the stator. The liquidcomponent 30, which can be an aqueous phosphate solution as describedabove, is introduced into one or more of the internal cavities 70b, 70cin the cavity pump 70 at a sufficient pressure, typically from about 50to 70 psi, to avoid ejection of the liquid 30 from the cavity. Theslurry 40 is then pumped through an impingement element M for furtherblending as described in connection with the previous embodiments. Theslurry 40 is then pumped through a constricting element 50, such as anozzle or other reduced diameter orifice, to be dispensed in atomizedform 45.

The cavity pump 70 preferably has at least four interior transientchambers.

As in the process described above, chopped fiberglass roving 80 can beadded to the atomized cementitious material 45 from a separate nozzle 95downstream from the constricting element 50. Alternatively, preselectedshort lengths of binderless fiberglass fibers 85 can be included in thedry material 10 that is added to inlet cavity 70a.

In an alternative embodiment of this process, illustrated in FIG. 3,inactive dry material 10i comprising predetermined amounts of silicondioxide and preselected lengths of binderless fiberglass fibers 85 canbe mixed with the liquid component 30 outside of the cavity pump 70 andthen introduced as a first mixture 41 into the cavity pump. The cavitypump 70 pumps the first mixture 41 to an impingement element M. Activedry material 10a, comprising predetermined amounts of magnesium oxide,calcium carbonate and one or more additional metallic oxides aspreviously described, is fluidized in pressurized gas stream 20 andintroduced to the impingement element M to form a slurry 40. Theresulting slurry 40 is then pumped through the impingement element M andthrough a constricting clement 50 to be mixed and atomized, aspreviously described. Chopped fiberglass roving 80 can be added to theatomized cementitious material 45 as described above.

The dry material 10 and the slurry 40 can be pumped through the cavitypump at pressures of up to 100 psi and flow rates of up to about 3,456in³ /min.

The following non-limiting example is presented.

EXAMPLE

The following raw materials were provided in the proportions indicated.All amounts are given in parts by weight.

    ______________________________________              Formulation                       Formulation                                  Formulation              I        II         III    ______________________________________    Silicon dioxide                100        40         30    Magnesium oxide                15         15         30    Monometal   40         80         120    phosphate (aq)    (50% conc.)    Aluminum oxide                6          3          12    Iron oxide  2          1          4    Calcium oxide                4          2          8    Potassium oxide                2          1          4    Titanium dioxide                --         1          --    Sodium oxide                --         --         1    Calcium carbonate                --         1          --    Fiberglass  8          --         15    ______________________________________

Each of Formulations I-III was processed using the dual receptacleprocess described above with respect to FIG. 1. The following wereutilized in the process:

Air pressure in fluidizing conduit: 35 psi

Dry material flow rate to fluidizing conduit: 648 in³ /min

Fluidizing conduit inner diameter: 1 inch

Liquid jet pressure: 60 psi

Liquid flow rate: 162 in³ /min

Liquid jet: 7/64 inch

Impingement element M: Static mixer with 1 inch bore

Constricting element 50: Nozzle with 3/4 inch orifice

The material was sprayed onto test panels and reached full cure within1/2 to 2 minutes after being sprayed.

Formulation I produced a cementitious material with a specific gravityof 1.7 and a compressive strength of about 5000 psi. This formulation isuseful, for example, as a replacement material for filled polyesterresins used, for example, in the manufacture of molded shower units andthe like. Formulation II produced a foam-like, lightweight structurewith a specific gravity of 0.8 and compressive strength of about 700-800psi. This formulation is useful, for example, in applications requiringfire-resistant and/or insulative structures such as panels, walls, andthe like. Formulation III produced a high-strength cementitious materialwith a specific gravity of 2.0 and a compressive strength of about30,000 psi. This formulation is useful, for example, in applicationsrequiring the manufacture of high-strength structural shapes.

Having now described a few embodiments of the invention, it should beapparent to those skilled in the art that the foregoing is therebyillustrative and not limiting, having been presented by way of exampleonly. Numerous modifications and other embodiments are within the scopeof one of ordinary skill in the art and are contemplated as fallingwithin the scope of the invention as defined by the appended claims.

What is claimed is:
 1. A continuous process for making a sprayable,rapid setting cementitious material, comprising the steps of:a) adding adry component to a first receptacle in fluidic communication with anddisposed upstream of a second receptacle, the first receptacle beingisolated from the second receptacle during addition of the dry componentto the first receptacle; b) isolating the first receptacle from ambientconditions forming a closed system; c) allowing the first and secondreceptacles to reach a substantially uniform pressure by introduction ofa pressurized gas to each of the first and second receptacles; d)permitting the dry component to transfer from the first receptacle tothe second receptacle when the first and second receptacles are atsubstantially equal pressures; e) continuously delivering the drycomponent into a fluidizing element in communication with the secondreceptacle in which the dry component is fluidized within a pressurizedgas stream; f) forming a slurry by introducing to the fluidized drycomponent an aqueous phosphate solution; and g) mixing and atomizing theslurry to obtain a sprayable, rapid setting cementitious material in theform of an atomized material.
 2. The process according to claim 1,wherein the dry component consists essentially of an active portion andan inactive portion, wherein the active portion comprises up to about 50parts by weight magnesium oxide, and the inactive portion comprises upto about 200 parts by weight silicon dioxide.
 3. The process accordingto claim 2, wherein the active portion further comprises up to about 200parts by weight of at least one metallic oxide selected from the groupconsisting of the oxides of calcium, aluminum, iron, potassium, titaniumand sodium, and up to about 50 parts by weight calcium carbonate, andwherein the inactive portion further comprises up to about 30 parts byweight of binderless fiberglass fibers.
 4. The process according toclaim 1 wherein the aqueous phosphate solution is selected from thegroup consisting of ammonium phosphate, monoaluminum phosphate,monomagnesium phosphate and monocalcium phosphate.
 5. The processaccording to claim 1 wherein the fluidizing element comprises a conduithaving a gas entry port for introduction of a gas and a liquid entryport for introduction of a pressurized liquid.
 6. The process accordingto claim 1 wherein the fluidizing element is in fluid communication withthe first and second receptacles to establish a substantially uniformpressure in the first and second receptacles and in the fluidizingelement.
 7. The process of claim 1 further including the step of addinga fiberglass material to the atomized material.
 8. A continuous processfor making a sprayable, rapid setting cementitious material, comprisingthe steps ofa) adding a dry component to an inlet port of a cavity pumpand operating the cavity pump to transport the dry component through thepump; b) separately introducing an aqueous phosphate solution to aportion of the dry component in an interior chamber in the cavity pump;c) transporting the dry material and the solution to an impingementdevice to form a slurry; and d) mixing and atomizing the slurry toobtain a sprayable, rapid setting cementitious material in the form ofan atomized material.
 9. The process according to claim 8, wherein thedry component consists essentially of an active portion and an inactiveportion, wherein the active portion comprises up to about 50 parts byweight magnesium oxide, and the inactive portion comprises up to about200 parts by weight silicon dioxide.
 10. The process according to claim9, wherein the active portion further comprises up to about 200 parts byweight of at least one metallic oxide selected from the group consistingof the oxides of calcium, aluminum, iron, potassium, titanium andsodium, and up to about 50 parts by weight calcium carbonate, andwherein the inactive portion further comprises up to about 30 parts byweight of binderless fiberglass fibers.
 11. The process according toclaim 9 wherein the aqueous phosphate solution is selected from thegroup consisting of ammonium phosphate, monoaluminum phosphate,monomagnesium phosphate and monocalcium phosphate.